1. Field of the Invention
The present invention relates to bypass guidance systems for conducting anadromous fish (e.g. salmon, American shad, blueback herring) as well as catadromous fish (e.g. eels) through dams and other man-made obstructions with maximum throughput and minimum stress to the migrating fish, as well as other migratory xe2x80x9csilver underbodiedxe2x80x9d fishes, such as smelt, including Delta Smelt found in California""s watercourses.
2. Description of the Prior Art
Through the world, land use associated with the development of dams and man-made lakes has adversely effected migrations of anadromous and catadromous fish. Where possible, for example at dams and their associated man-made lakes, bypass facilities have been built on the surface, overhead and submerged to facilitate migration particularly for anadromous fish, both for juveniles in the downstream direction and for adults in the upstream direction.
However, since there usually exist many such dams and lakes separating the ocean from spawning and rearing habitat, the time table of natural migration can be unduly prolonged by the presence of these obstacles. The bypass facilities constructed both at low-head and high-head dams to mitigate their adverse effect on migrating fish include but are not limited to the following: trapping and hauling, bypass or fishways, ladders or locks and fish elevators. More often than not, these bypass facilities inadvertently frighten fish, preventing the fish, particularly juveniles, from approaching the bypass facility in large numbers, and thus lead to little or no benefit despite the large costs involved. As a result, not only are many of the existing bypass facilities ineffective, but in addition most are also time consuming thereby unduly prolonging fish migration. Moreover, migrating juveniles and adults often fall easy prey to overhead and/or submerged predators at the termini of bypass facilities due to the means or methods employed. That is to say, no single fish bypass facility has yet been demonstrated to be biologically effective, practical to install and operate, and acceptable to environmental groups, or State or Federal agencies under the variety of site conditions outlined above.
It is an object of the present invention to provide an effective method and system for guiding anadromous fish (e.g., salmon, steelhead, American shad, blueback herring) as well as catadromous fish (e.g. eels and as well Delta Smelt and similar fish) past dams, cooling and irrigation intakes, and other man-made obstructions.
Another object of the present invention is to guide such fish using their previously unrecognized natural responses to environmental stimuli.
One aspect of the invention enhances passage through dams and other man-made obstructions by artificially recreating at the water surface conditions associated with safe and/or hazardous aspects of the aquatic environment to entice migrating fish along a pre-selected and desired path.
Another aspect of the present invention is that it is capable of operating synergistically with presently existing systems for aiding fish migration, including but not limited to angled barracks positioned at entry basins, fixed screens of various shapes and orientations, velocity limiters, sluiceways, spillways, traveling screens, barrier nets and other facilities presently known to those skilled in the art, which are employed to reduce entrainment of the migrating fish in hydraulic turbines. The present invention can be advantageously combined with such conventional bypass facilities. For example, an existing fish ladder or bypass which may be combined with the present invention to safely transport the fish downstream. Trash sluiceways may also serve to transport screened fish downstream if associated with a bypass guidance system in accordance with the present invention.
Artificial environments that mimic naturally occurring conditions are surprisingly useful in eliciting a response that guides fish along a selected three-dimensional (3D) path around an obstacle in a relatively swift and low cost practical manner. It has been established that the selection criteria used by fish in choosing a path is based, inter alia, on a learned response that occurs usually during schooling in the fishes"" natural (not artificial) habitat.
The present invention guides anadromous fish with a series of disturbed (or rippled) air-water interface regions contiguously arranged in a selected first direction across the air-water interface at a bypass entry basin adjacent to an obstruction such as a dam or lake. The ripples are preferably directed along the desired guidance path. The last disturbed interface region preferably has a narrowed exit that leads to the bypass facility. At each of these disturbed interface regions, artificial or natural light, diffusely refracted as it passes through the disturbed surface of the water, elicits a learned response from fish by establishing an aura-dominated passage which xe2x80x9csilver underbodiedxe2x80x9d fish generally perceive as being safe because diffuse refracting light obscures their presence from any predator that may be present below or above the disturbed interface region. At the outlet of the bypass facility, another series of disturbed (or rippled) air-water interface regions is again established along a second direction at the exit basin together with artificial or natural light refracting from the disturbed surface of the water to again elicit the learned response described above. However, the size of the entry to the bypass guidance system at the outlet from the bypass facility reverses from that previously described at the entry thereto. That is, the entry to the bypass guidance system at the outlet from the bypass facility is narrow while the exit is large.
In one embodiment, the present invention includes a series of shower assemblies arranged in the selected first direction for the purpose of spraying fluid in a pre-selected pattern to creates the above-mentioned series of disturbed air-water interface regions. This creates a 3D path which xe2x80x9csilver underbodiedxe2x80x9d fish usually perceive as being safe because they are hidden from view by diffuse refraction of light at the disturbed air-water interface regions. Thus nearly all xe2x80x9csilver underbodiedxe2x80x9d fishes can be guided by systems in accordance with the present invention. The shower assemblies can be provided in various different arrangements and in associations with various artificial and natural elements as described in greater detail below.
For example, if the entry and exit basins at an obstruction such as a dam or lake is narrow, an overhead cable can be stretched across the basin in a selected direction starting at a bank adjacent to the bypass facility and ending at an opposite bank. This cable carries a series of lamp and shower assemblies cantilevered from the cable at selected locations. In operation, the lamp and shower assemblies create the above-mentioned series of disturbed air-water interface regions across the entry basin leading to the bypass facility. The area of the spray and illuminated regions can vary, preferably with them being largest at the entryway and smaller at the exit end or vice versa depending upon whether the bypass guidance system is located at the bypass facility""s entry or exit basin, respectively. The combined disturbed interface regions can be arranged to establish a tapering or triangularly-shaped outline for the contiguous disturbed regions when they are viewed from above. In the entry basin, the triangularly-shaped outline has an apex near the entrance to the bypass facility. In the exit basin, the triangularly-shaped outline of the bypass guidance system reverses with its entrance being at the apex of a triangularly-shaped outline near the outlet from the bypass facility. Preferably the fluid applied to disturb the air-water interface regions is water, but could be compressed air.
In another embodiment, a series of buoys are anchored to the bottom of the basin in the selected direction. Each buoy includes an L-shaped tubular support having a far leg which extends above the air-water interface. A near leg of the tubular support extends from a base that is open to water intrusion and contains a pump that is energized by a power source located outside the basin. The far leg of the L-shaped support includes lamp and shower assemblies, the latter being operationally connected to the pump through the near leg to receive water, the preferred fluid for creating the disturbed air-water interface regions.
In yet another embodiment, the bypass guidance system includes a series of floating rafts moored along the selected direction, that preferably have four pontoons arranged to form a quadrilateral. Each raft includes a floor and an L-shaped support having a first leg that is attached to and extends through the floor of the raft into the water. A pump is attached to the L-shaped support to supply water to a shower assembly positioned in the second leg of the support that cantilevers from the raft. A lamp assembly is also attached at the tip of the second leg.
In still another embodiment, the rafts have blackened-undersides and also include supports which allow placing a secondary lamp sub-assembly below the air-water interface. It appears that light directed upwardly toward a blackened-underside creates a hostile environment for migrating xe2x80x9csilver underbodiedxe2x80x9d fish thereby directing the fish along the correct aura-dominant path established by the disturbed regions and lamps. That is to say, to keep the migrating fish on the correct path and to deter them from circling back in a vertical plane through the series of rafts thereby prolonging their migration, the secondary lamp sub-assemblies are cantilevered from the back side of the raft away from the direction of fish migration to create the aforementioned hostile environment.
Still another embodiment employs a grid of shower and lamp assemblies, split into separate rows, positioned along a series of parallel cables spanning the basin. Arranging progressively longer rows of shower and lamp assemblies further away from the entry to or exit from the bypass facility establishes the previously described triangularly-shaped outline for the bypass guidance system. In the entry basin, the triangularly-shaped outline includes a base row comprising shower and lamp assemblies followed by one or more additional rows of shower and lamp assemblies that are progressively closer to the entry to the bypass facility. Each successive row of shower and lamp assemblies is shorter that the preceding one. Note that as before the triangularly-shaped outline has an apex near the exit for the fish. In the exit basin when viewed from above the triangularly-shaped outline has its apex located the outlet from the bypass facility.
In the above embodiment, a canopy having a triangularly shaped aperture which complements the triangularly-shaped outline of the aura-dominated region created by the bypass guidance system can be stretched across the grid of cables. Such a canopy shades the water from above except in the aura-dominated, safe environment for xe2x80x9csilver underbodiedxe2x80x9d fishes thereby enhancing that area""s attractiveness. Concurrently, the dark area around the aura-dominated region concurrently establishes a safe environment for dark colored eels which facilitates their migration.
Still another embodiment of the present invention separates the lamp and shower assemblies by placing one or other type of assembly along a bank of the basin and the other type of assembly on rafts adjacent to the bank to establish a bypass guidance path between the rafts and bank.
Still another embodiment of the present invention, instead of using a plurality of the series of diagonal cables, uses a series of rafts arranged along separate but parallel paths to form diagonal columns of a grid of shower and lamp assemblies. Each raft carries cantilevered supports to which the shower and lamp assemblies attach. The cantilevered supports each have a first section that extends from one side of the rafts above the water facing the migrating fish. In this embodiment, a series of previously mentioned secondary lamp sub-assemblies direct light in a upwardly directed pattern that creates the aforementioned hostile environment for the anadromous migrating fish. That is to say, to keep the migrating anadromous fish on the correct path and to deter them from circling back along a vertical plane through the rafts, the secondary lamp sub-assemblies are cantilevered from the back side of the raft away from the direction of fish migration to create the aforementioned hostile environment. The last diagonal raft of the grid is located adjacent to the bypass facility. In the exit basin a plan view of the rafts"" arrangement reverses.
Submerged lights that illuminate the underbody of anadromous fish repel them from an area or obstacle, such as a pump or turbine intake, and may be placed in a wide area to establish a boundary of which the fish will not cross. Mercury lamps are useful for this purpose, or lamps generating sufficient radiation to prevent aquatic growth on their surface.
For catadromous fish, the present invention elicits the desired response by artificially creating a series of disturbed shadowed or dark air-water interface regions contiguously arranged in a selected direction or directions across a bypass facility""s entry basin adjacent to the obstruction to be traversed. The bypass guidance system includes a narrowed exit at the last disturbed interface region that leads to a holding tank. The holding tank is located opposite the bypass facility around the obstruction used by the anadromous fish. In the air above the boundaries of the disturbed regions, canopies can be stretched as described above to create the darkened shadowed interface regions at the air-water interface. Alternatively, a series of rafts can be deployed at the air-water interface to produce the same result. It appears that the darkened interface regions stimulate catadromous and dark colored, or dark colored, fish to elicit a learned response that the shadowed-dominated passage is a safe since it hides their presence from predators. At the exit of the holding tank, the series of disturbed shadowed interface regions is again created along a second direction, to again elicit the previously described response. However, the size of the entryway and exit at the exit from the holding tank is reversed over that previously mentioned. That is, the entryway is narrow and the exit is large. As a result, the passage of catadromous fish becomes surprising rapid.
In many cases, the exit of the holding tank is directly connected to the opposite basin so that the catadromous fish are easily transported. Or the exit of the holding tank could be blocked and catadromous fish trapped. In this way catadromous fish can be hauled around the obstruction, or the trapped catadromous fish could be disposed of commercially or in appropriate manner if such fish are determined to be deleterious to the existence of the anadromous fish in concomitant migration therewith.
An advantage of the present invention is that it advantageousy reduces head loss at power-generating dams during intervals of downstream migration. During such intervals, power generating dams using conventional fish bypass facilities may have to divert significant quantities of water from power generation into the bypass facility to ensure safe passage of migrating fish. Guiding fish more effectively into the bypass facility using a much smaller quantity of water increases the productivity of power generating dams.
These and other features, objects and advantages will be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures.